Method for clarifying titanium sulphate solutions

ABSTRACT

A process for the clarification of the black liquor obtained in the acid leaching of titaniferous ores and titanium slag feed, which process comprises adding to the black liquor a watersoluble cationic polymer flocculant containing monomer units having the formula:   WHEREIN R&#39;&#39; is hydrogen or methyl and R1 and R2 are alkyl groups, for example methyl or ethyl groups and preferably contain not more than four or five atoms.

Ilnited States Patent n91 Manfroy et al.

[ 1 March 6, 1973 METHOD FOR CLARIFYING TITANIUM SULPHATE SOLUTIONS [22] Filed: Nov. 2, 1970 [21] Appl. No.: 86,337

[30] Foreign Application Priority Data Nov. 5, 1969 Great Britain ..54,285/69 [52] US. Cl. ..423/544, 423/558, 423/610, 210/54 [51] Int. Cl. ....C01g 23/00, COlg 23/04, COlg 49/14 [58] Field of Search ..23/117; 209/5; 210/54; '423/544, 566, 659, 610, 615, 558

[56] References Cited UNITED STATES PATENTS 2,831,841 4/1958 Jones ..210/54 UX 2,767,053 10/1956 Griffin et al ..23/117 3,507,847 4/1970 Williams et al. ..210/54 X 3,503,946 3/1970 Scanley et al ..210/54 X 3,488,720 1/1970 Nagy et al. ..210/54 3,147,218 9/1964 Booth et al. ..210/54 FOREIGN PATENTS OR APPLICATIONS 1,570,656 6/1969 France ..23/202 R 1,184,053 3/1970 Great Britain ..23/117 Primary Examiner-Edward Stern Attorney-Griswold & Burdick and Richard W. Hummer [5 7] ABSTRACT A process for the clarification of the black liquor obtained in the acid leaching of titaniferous ores and titanium slag feed, which process comprises adding to the black liquor a water-soluble cationic polymer flocculant containing monomer units having the formula:

wherein R is hydrogen or methyl and R, and R are alkyl groups, for example methyl or ethyl groups and preferably contain not more than four or five atoms.

14 Claims, No Drawings METHOD FOR CLARIFYING TITANIUM SULPHATE SOLUTIONS The present invention relates to a process for clarifying the black liquor" obtained in the acid leaching of titaniferous ores and titanium slag feed.

In the production of titanium oxide from a titanium containing source, which is generally ilmenite ore and/or titanium slag feed, sulphuric acid is used to leach the titanium from the source to give a suspension, which, before settling, is generally termed black liquor. The process of separating the residue of the titanium source from the suspension is generally known as black liquor clarification.

According to the present invention there is provided a process for clarifying the black liquor obtained in the acid leaching of a titanium containing source which comprises adding to the black liquor a water-soluble cationic polymer flocculant containing monomer units having the formula:

wherein R is hydrogen or methyl, and R and R are alkyl groups, for example, methyl or ethyl groups, and preferably contain not more than four or five carbon atoms.

The water-soluble cationic polymer flocculant may be prepared by reacting together an acrylamide containing polymer, a secondary amine of the formula:

wherein R and R are each alkyl groups, and formaldehyde. Optimum results are obtained when the reaction is carried out to give substantially 100 percent conversion of the NH sites of the polyacrylamide to NH CH NR,R Although a proportion of the acrylamide groups of the polyacrylamide may be hydrolyzed e.g. to sodium carbonylate groups, the best results are obtained when none of the acrylamide groups are hydrolyzed. An increase in the number of hydrolyzed acrylamide groups in the flocculant used in the process of the invention leads to an increase in the settling rate, but a decrease in the clarity of the supernatant liquid obtained.

The cationic polymer flocculant should preferably contain 50 mole percent of aminated acrylamide monomer units, although polymers containing as little as H) percent aminated acrylamide monomer units may be used. In some instances polymers containing 80 or even 100 mole percent aminated acrylamide units are used. Preferably, the acrylamide polymer used in the process of the invention has a molecular weight between 1 million and5 millions.

Examples of suitable acrylamide containing polymers are polymethacrylamide, copolymers of acrylamide with acrylic acid, methacrylic acid, alkali metal salts of the foregoing acids, styrene sulfonate, nvinyl-pyrrolidone, N-vinyl-pyridine, 2-aminoethyl acrylate and copolymers of acrylamide or methacrylamide with up to 50 mole percent of water-insoluble monomers such as methyl acrylate, methyl methacrylate, acrylonitrile, styrene, vinyl methyl ether and vinyl acetate. The preferred cationic polymer flocculants for use in the practice of the present invention are based "5 on the acrylamide polymers exemplified above.

The secondary amine used in the amination of the acrylamide polymer has the formula:

wherein R and R are alkyl groups, preferably containing not more than four or five carbon atoms. Preferred secondary amines are dimethylamine and diethylamine. These secondary amines maybe used in the form of their acid salts, for example their hydrochlorides in the amination of the acrylamide containing polymer.

In the practice of the invention, the cationic watersoluble polymer flocculant is desirably mixed rapidly with the black liquor mineral suspension. Thus optimum results are achieved when high shear conditions exist at the black liquor. The agitation may, if required, be continued during subsequent floc building.

Preferably, the polymer flocculant is added as an aqueous solution having a concentration of 0.05 percent to 1 percent, for example, about 0.1 percent. it is suitably added to the black liquor just before the latter enters the clarifier.

Good results are obtained using the process of the present invention when the polymer flocculant is added in an amount of 25 to 150 grams, preferably 50 to 75 grams, of polymer flocculant per cubic meter of the black liquor.

In the manufacturing of titanium dioxide pigments by dissolving titanium-containing minerals in strong sulfuric acid for subsequent precipitation of TiO two typical raw material sources are used, i.e. ilmenite whether it be concentrated or not and a slag coming from iron titaniferous of t:tan:Ferous iron ore.

Both minerals differ in titanium and iron content. in the process of clarification of the so called black liquors easiness of settling and clarification will also differ completely as well as the addition rates of synthetic or natural flocculation agents.

The invention is further illustrated by the following Examples.

EXAMPLE I A 100 ml sample of black liquor" slurry coming from the sulfuric acid extraction of 100 percent Western Australian ilmenite preliminarily reduced by iron scrap, temperature 65C, solid content 40 g/l, density of liquor 1.60, is poured into a l liter beaker, equipped with a mechanical stirrer. The stirrer is rotated at such a velocity as to create a 2 3 cm vortex in the beaker.

The polymer used in this Example is a water soluble cationic polymer flocculant prepared by reacting together an acrylamide containing polymer having the following characteristics:

Ratio acrylate to acrylamide groups:

4 7 percent V Viscosity of a 0.5 percent solution at pl-I3 at 25C measured by an Ostwald capillary viscosimeter:

, 8 12 cps with a secondary amine of the formula:

/Clh llN C Ha and an aldehyde of the formula:

Molar ratio polymer to amine and aldehyde:

1 mole polymer 0.75 mole amine and aldehyde.

An aqueous solution of the polymer is diluted to an active polymer concentration of 0.5 percent by weight. An addition of 30 milliliters of the above solution (containing 100 mg of this diluted polymer) is injected into the black liquor drop by drop. When addition is completed a further 30 seconds stirring is provided at the same speed.

The flocculated slurry is poured into a 1 liter graduated cylinder and allowed to settle. The speed of settling is recorded. After 1 hour 100 ml of the supernatant liquid at the 700 ml mark is extracted and the solids concentration is measured.

The same technique is used at various polymer addition rates and results are tabulated in Table l.

The settling rate is measured according to the standard technique i.e. by measuring the tangent in the free fall zone of the sedimentation curve obtained by plotting settled sledge volume versus time.

The clarity is measured by filtration of the 100 ml extracted supernatant liquid and by determination of the increased weight of the dry filter medium.

Units: mg/l: (polymer addition rate):

mg lOO percent active polymer per-liter slurry to be flocculated m/h (settling rate): speed at which flocculants settle into the cylinder mg/l (clarity): mg solids per liter of slurry.

TABLE 1 Australian ilmenite 100%) The same testing technique as used in Example 1 is applied on an industrial so called black liquor coming from the acid leaching of a titaniferrous slag having the following main characteristics:

Tests were made with four different polymers covered by the present invention and respectively called A, B, C and D. Results are summarized in Table 2.

Polymer A corresponds to the polymer of Example 1.

Polymer B is an acrylamide containing polymer having the I following characteristics: Ratio acrylate to acrylamide groups: 25 35 percent, viscosity of a 0.5 percent solution at pl-l7, 25C, containing 4 percent by weight NaCl, measured by an Ostwald capillary viscosimeter: l2-l6 cps. The reaction corresponds to that of polymer A.

Polymer C is prepared from the starting polymers and chemicals corresponding to polymer A with a molar ratio of polymer to amine and aldehyde of l l.

Polymer D is a copolymer of acrylamide and quaternary (Z-trimethylamine)-ethylacrylate chloride.

TABLE 2 Polymer Addition rate Settling rate Clarity mgll m/h Clarity A 50 9.3 good A 40 9.3 good B 50 17.5 good C 50 9.7 good D 50 5.2 good D 75 8.5 good The statement good in clarity" means less than mg/l solids after 1 h in the supernatant liquor according to the testing technique of Example 1.

EXAMPLE 3 The same testing technique as used in Example 1 was applied to a black liquor coming from the sulfuric acid leaching of a Norwegian ilmenite.

The results are summarized in Table 3.

In a titanium dioxide pigment plant'employing sulfuric acid leaching, using a blend of Australian ilmenite and slag as raw material the polymer according to Example was tested on a larger scale.

characteristics of the black liquor: Temperature: Solids content: 50 g/l TiO, content:

Acid to Tio, ratio TABLE 4 Polymer addition Concentration of Settling rate rate mg/l (l%) ta overflow underflow m/h (after 2 h) mg/l The thickened underflow of this clarification and settling test is strongly flocculated and remains so during the whole washing or elutriation process. If needed very small additional amounts of the polymer can be added to increase the settling speed and clarity of the elutriated sludge and supernatant liquid.

In industrial practice small amounts of polymer of 5 mg/l can be added to the sludge during elutriation to provide an almost solid free 10 mg/l) supernatant liquid in the clarifiers.

We claim:

I. A process for the clarification of the black liquor obtained in the acid leaching of a titanium containing source which process comprises mixing with the black liquor under high shear conditions an amount of a water-soluble cationic polymer flocculant containing monomer units having the formula wherein R is hydrogen or methyl, and R and R are alkyl groups to provide from 25 to 150 grams of the polymer flocculant per cubic meter of the black liquor.

2. A process as claimed in claim I wherein R, and R individually do not contain more than five carbon atoms.

3. A process as claimed in claim 1 wherein R and R individually are methyl or ethyl groups.

4. A process as claimed in claim 1 wherein the watersoluble cationic polymer flocculant is prepared by reacting together an acrylamide-containing polymer, a secondary amine of the formula: wherein R and R are each alkyl groups, and formaldehyde.

5. A process as claimed in claim 4 wherein the reaction is'carried out to give substantially 100 percent conversion of the NH, sites of the polyacrylamide to NH'''CH2NR1R2- 6. A process as claimed 11'] claim 4 wherein the secondary amine alkyl groups individually do not contain more than five carbon atoms.

7. A process as claimed in claim 4 wherein the secondary amine employed is dimethylamine or diethylamine.

8. A process as claimed in claim 4 wherein the acrylamide-containing polymer is polymethacrylamide, a copolymer of acrylamide with acrylic acid, methacrylic acid, an alkali metal salt of the foregoing acids, styrene sulfonate, N-vinyl-pyrrolidone, N-vinylpyridine, or, a copolymer of acrylamide of methacrylamide with up to 50 mole percent of methyl acrylate, methyl methacrylate, acrylonitrile, styrene, vinyl methyl ether or vinyl acetate.

9. A process as claimed in claim 1 wherein the watersoluble cationic polymer flocculant contains from 10 to 100 mole percentaminated acrylamide monomer units.

10. A process as' claimed in claim 1 wherein the water-soluble cationic polymer flocculant contains 50 mole percent aminated acrylamide monomer units.

11. A process as claimed in claim 4 wherein the acrylamide polymer used has a molecular weight between 1 million and 5 millions.

12. A process as claimed in claim 1 wherein the high shear conditions are maintained during subsequent floc building.

13. A process as claimed in claim 1 wherein the water-soluble polymer flocculant is added to the black liquor as an aqueous solution having a concentration of 0.05 to 1 weight percent.

14. A process as claimed in claim 1 wherein the water-soluble polymer flocculant is added to the black liquor in an amount of from 50 to grams of polymer flocculant per cubic meter of the black liquor. 

1. A process for the clarification of the black liquor obtained in the acid leaching of a titanium containing source which process comprises mixing with the black liquor under high shear conditions an amount of a water-soluble cationic polymer flocculant containing monomer units having the formula
 2. A process as claimed in claim 1 wherein R1 and R2 individually do not contain more than five carbon atoms.
 3. A process as claimed in claim 1 wherein R1 and R2 individually are methyl or ethyl groups.
 4. A process as claimed in claim 1 wherein the water-soluble cationic polymer flocculant is prepared by reacting together an acrylamide-containing polymer, a secondary amine of the formula: wherein R1 and R2 are each alkyl groups, and formaldehyde.
 5. A process as claimed in claim 4 wherein the reaction is carried out to give substantially 100 percent conversion of the NH2 sites of the polyacrylamide to -NH-CH2-NR1R2.
 6. A process as claimed in claim 4 wherein the secondary amine alkyl groups individually do not contain more than five carbon atoms.
 7. A process as claimed in claim 4 wherein the secondary amine employed is dimethylamine or diethylamine.
 8. A process as claimed in claim 4 wherein the acrylamide-containing polymer is polymethacrylamide, a copolymer of acrylamide with acrylic acid, methacrylic acid, an alkali metal salt of the foregoing acids, styrene sulfonate, N-vinyl-pyrrolidone, N-vinylpyridine, or, a copolymer of acrylamide of methacrylamide with up to 50 mole percent of methyl acrylate, methyl methacrylate, acrylonitrile, styrene, vinyl methyl ether or vinyl acetate.
 9. A process as claimed in claim 1 wherein the water-soluble cationic polymer flocculant contains from 10 to 100 mole percent aminated acrylamide monomer units.
 10. A process as claimed in claim 1 wherein the water-soluble cationic polymer flocculant contains 50 mole percent aminated acrylamide monomer units.
 11. A process as claimed in claim 4 wherein the acrylamide polymer used has a molecular weight between 1 million and 5 millions.
 12. A process as claimed in claim 1 wherein the high shear conditions are maintained during subseqUent floc building.
 13. A process as claimed in claim 1 wherein the water-soluble polymer flocculant is added to the black liquor as an aqueous solution having a concentration of 0.05 to 1 weight percent. 